In recent years, there has been a dramatically increasing demand for infrared cameras not only for temperature measurement but also for security purposes. Examples of known infrared cameras include quantum-type infrared cameras and bolometer-type infrared cameras. A quantum-type infrared camera normally requires cooling so as to cope with thermal noise, and therefore, the infrared camera becomes larger in size and more expensive. A bolometer-type infrared camera that detects resistance changes due to heat also requires cooling by a Peltier device in practice, and further requires a large-capacity memory for periodic calibration of each pixel. Moreover, such a bolometer-type infrared camera has a problem that images become discontinuous at the time of calibration. In addition to that, a bolometer-type infrared camera has the problems of being easily affected by background radiation, consuming a large amount of power, being expensive, being large in size, and being heavy.
To solve such problems, JP 2009-042164 A discloses an infrared camera using surface plasmon resonance phenomena, for example. Using a prism, this infrared camera detects a change in the permittivity of a dielectric film due to heat as a change in the metal surface plasmon resonance condition. Also, JP 5-273503 A discloses a spatial light modulator that uses surface plasmon resonance and is capable of high-efficiency light modulation without conversion of optical information to electrical information, or more specifically, a spatial light modulator formed with an optical wave coupler including a composite layer of a material having a refractive index that varies with light irradiation and a metal.